Using a battery maintainer, I get 7 or 8 years out of an AGM battery in my dump trailer. I can replace it 3 times with the money I would spend on a Lithium battery. It would take 20 - 25 years to break even, and I doubt the lithium would last that long. By then, there will likely be better battery technology available. IMO, in addition to the economics, it isn't worth the problems associated with lithium at this point.
I do however use a lithium cordless tool battery to power the trailer emergency braking systems on my other trailers though. The small lead acid batteries always seem to go dead when the trailer isn't used frequently. I just charge the tool battery once a season. It holds a charge better than the lead acid battery.